SEROTYPING OF BACTERIAL ISOLATES
DE Public Health Laboratory serves the state of Delaware as a referral center for serotyping bacterial isolates when necessary to confirm and/or establish clinical significance or for epidemiological tracking purposes. Antisera and appropriate quality control measures may often not be available to local laboratories, and this service is provided by DPHL with the assistance of CDC or other reference laboratories.
- E.coli 0157:H7
- Vibrio cholerae
- Haemophilus influenzae, type b
- Neisseria meningitidis subtypes
SAMPLE COLLECTION, HANDLING AND SHIPMENT
- Isolates should be submitted as pure, fresh subcultures on a media appropriate to support the test organism (e.g. BHI, TSI, Chocolate slants). Note that tubed media is preferred.
- Complete the Test Requisition Form including patient information or order request on-line through our Laboratory information management system (LIMS). Specimen and forms should be placed in a designated location at each site for the lab courier to pickup.
- If referral to CDC is likely, or specifically requested, a completed CDC dash form must accompany the specimen.
- Specimens should be transported by courier in appropriate double-tubed biohazard containers. These containers can be requested from the laboratory.
SALMONELLA/SHIGELLA - both agents of gastroenteritis associated with food or water-borne contamination. Diagnosis is based on original isolation and identification of bacteria, usually from stool or blood. Because many different serotypes can be present in a community at the same time, isolates are submitted to State Lab for serotyping in order that the State Epidemiology Dept can track isolates in cases of outbreaks. All isolates are also reported to CDC through DERSS, an epidemiology tracking computer program designed to transmit results directly by the internet. All Salmonella isolates are sent to our Environmental Molecular Lab for Pulse-field Gel Electrophoresis (PFGE) where fingerprinting of the bacteria is done and patterns are examined by CDC's Pulsenet for outbreak identification. Isolates are sent to CDC's National Antimicrobial Resistance Monitoring system (NARMS) based on sampling criteria provided by CDC.
E.COLI 0157:H7 - agent of enterohemorrhagic gastroenteritis, usually causing bloody diarrhea and hemolytic uremic syndrome associated with a toxin produced by this strain of E. coli. Differentiation by serotyping from other normal E. coli is necessary for definitive identification from a stool specimen. All EHEC isolates are sent to our Environmental Molecular Lab for Pulse-field Gel Electrophoresis (PFGE) where fingerprinting of the bacteria is done and patterns are examined by CDC's Pulsenet for outbreak identification. Isolates are sent to CDC's National Antimicrobial Resistance Monitoring system (NARMS) based on sampling criteria provided by CDC.
VIBRIO CHOLERAE - Serotyping of isolates is important in differentiation of true cholera (serogroup 01, toxin-related) from non-toxogenic strains (non group 01) which are usually associated with ingestion of warm water seafood. Isolates are sent to CDC's National Antimicrobioal Resistance Monitoring system (NARMS) based on sampling criteria provided by CDC.
HAEMOPHILUS INFLUENZAE, TYPE B - This serotype is a common cause of meningitis in children.
NEISSERIA MENINGITIDIS - Meningococcus is a highly infectious cause of meningitis. Since many serogroups are possible, it is important to serotype in cases of possible outbreaks. Serogroups B & C are most common in the U.S.
Turnaround time is dependent on test requested, status of specimen on receipt (quality, quantity, purity) and the need for preliminary testing prior to serotyping.
Results are usually available within 1 week, however STAT requests can be accommodated with appropriate communication to the Clinical Microbiology Department.
Samples will be rejected if they are:
- Unlabeled - All specimens MUST have a unique patient identifier.
- Insufficient in Quantity - No specimen received, no specimen in container, or insufficient specimen to perform testing.
- Not Viable - Appropriate transport media and fresh isolates will ensure cell viability.
- Damaged - Specimen leaked or broken in transit.
Control of Communicable Diseases in Man, 15th edition, 1990.
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